In saying this, you might mean, "When do kittens start eating solid food?" and if that is the case, here is the answer:
In the wild, kittens start eating solid food at about seven weeks. Their mother shows them how to hunt and what to eat by bringing them killed or half-dead prey. Domesticated cats might not be able to bring in prey; their human owners usually go for the recommended age for beginning the weaning process: five weeks. But at seven weeks, the kitten should be fully confident with eating solid food. During their eighth week, the kittens will suck on their mother's leftover milk, but aren't entirely dependent on it anymore.
6 - 8 weeks. They start eating and learn to use the litter by then.
By not eating or drinking water for a long period of time:)
Shorthairs take 8 to 10 days, Longhairs take 10-14.
Until the kittens are weaned.
Until you run out of grass!!
Yes, they do. Sometimes they are more patient, and wait until you suspect nothing. Cats have long memories and can hold a grudge for a long time. So be nice to them.
You will gain weight much more rapidly if you start eating 2000 calories a day of you have been starving yourself beforehand. If you want to start eating a healthy amount of calories again you need to work up to it slowly, you should start eating a little more each day until you feel your eating enough. hope it helps (im no expert)
Probably until 15. Normal age for a cat.
8-22 Hours
Until they start breathing again or until help arrives. Otherwise, as long as you physically can.
Immediately.
2 or 3 weeks